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Inter MSC HO Issue

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  • #55763 Reply
    AAK
    Guest

    Dear All

    I am facing an issue of Inter MSC HO.
    The problem is that from the stats point of view, Incoming HO Stats are around 95 % while outgoing HO stats are around 20%.
    Now these stats are cell to cell. For example, we have the following scenario
    on 11 Feb,
    1. Cell A handovers(Inter-MSC) 1000 attempts to Cell B.
    2. In cell A stats, there are 1000 outgoing attempts and only 150 successful
    3. In cell B Stats, there are 1000 Incoming attempts and 950 are successful

    Now , we have done DT and found that mostly the HO are successful
    DT is reflecting the Incoming HO Stats.
    But now the issue is why outgoing HO is bad and is around 20%.
    Is it RF issue or NSS issue.
    Also, if we see the signalling, the source MSC gets the completion of HO from target MSC after HO is complete at target MSC. So is it that target MSC do not give final response to source MSC

    Kindly Help out

    Thanks

    #55764 Reply
    Pix
    Guest

    Check the RF side.
    If it’s ok (I’m sure it’s ok, because a failure of 80% is way too high to be just a RF problem), then you can assume the problem lies in the NSS.

    Check LAC definition in both MSC, check cell definitions, etc. good luck, it’s quite a pain.

    #55765 Reply
    AAK
    Guest

    Everything checked on definition part.
    My point is that the issue is from the stats point of view.

    From cell A to cell B on the same hour and same day

    Outgoing Stats in Cell A are 20 %
    Incoming Stats in Cell B are 95 %

    Same no of HO attempts but less no of successful HO

    #55766 Reply
    Pix
    Guest

    Here you could check if the HO REQUEST on one side is well sent to the target MSC. If it isn’t then it proves there is an issue.
    I’m sure you can diagnoze exactly when is the problem in the message flow, thanks to counter, and then deduce the exact point where the message is not flowing through.

    But it’s highly dependent on the vendor implementation of counters. In alcatel, we have incoming and outgoing request, attempts and success. Really useful to see at what step the problem is.

    Are you looking at the HO between just two cells, or is it the total amount of HO of one cell? I mean.. the 20% success is towards only one cell, or towards several cells?

    #55767 Reply
    AAK
    Guest

    Dear PIX

    Thanks for the reply

    Now as u asked, 20% HSR is only with one cell. With other cells HSR is OK

    Yes, you are right that we can see the exact flow and counters are always there to help us regarding that flow.
    We have already found following results but ……..

    Cell A(MSC A) have 1000 HO commands to Cell B(MSC B).

    and following is the sequence of counters regarding the signaling

    1. Cell A Outgoing HO command
    2. Cell B Incoming HO command
    3. Cell B Successful Incoming HO
    4. Cell A Successful Outgoing HO

    Now all is OK till 3 but step 4 is that Target MSC send ACK for successful HO and to release the channel to source MSC. Source MSC after recieving ACK from target MSC then peg Counter at Step 4 and after that releases the channel but source MSC just peg only 20%

    So we have the issue at step 4.
    so we can say that it is MSC-MSC signaling issue

    But we have a site that its 2nd sector Outgoing HSR is 99 % and its 3rd sector Outgoing HSR is 20%.
    Note that i am talking on CELL-CELL HSR basis.

    Now both these sectors doing InterMSC HO with the same cell B
    so if we name site
    1234 – Source site
    5678 – Target site

    so this is the HSR scenario

    21234-(InterMSC HO with)-15678 = 99 %
    31234-(InterMSC HO with)-15678 = 20 %

    Hope i am able to explain the exact issue.
    If there would be any attachment would have attached Signaling flow from which very easy to understand ๐Ÿ™‚

    Now WHAT CAN BE THE ISSUE ๐Ÿ™
    if it would have been MSC-MSC issue that all cells should face the same scenario. (HSR failure scenario)

    PIX, kindly understand and give some suggestions.
    Still any query kindly feel free to ask

    Really in need

    BR

    #55768 Reply
    TNS
    Guest

    Hi, AAK.

    HSR = 20% but what is the number of succ HO and do you have a distribution of the unsucc HO ( BSS probl, drop, ROC, preparation… )?

    BR

    #55769 Reply
    Pix
    Guest

    AAK,

    ok, i’ll have a look on monday, but your explanations are confusing at first glance ๐Ÿ™‚
    You’re saying that your counteers are measuring only 4 steps:

    1. Cell A Outgoing HO command
    2. Cell B Incoming HO command
    3. Cell B Successful Incoming HO
    4. Cell A Successful Outgoing HO

    For each step: what is the message counted by counter ?
    what is the measured value between the two cells only (source cell and target cell), not taking into account other neighbors.

    See ya !
    and thanks for sharing all this.

    Don’t worry, i’ll read all of it on monday more precisely. No need to repeat everything else.

    #55770 Reply
    kamal
    Guest

    Check the status of SCCP..
    Somtimes smaller things that we ignore can cause a lot..!

    #55771 Reply
    Sudheer
    Guest

    AAK,

    you can put both source & target cells under HO observation for some time in MSC’s and check the trace report to get some clue.

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